As photos from the surface and orbit have shown us, the principal erosion process on Mars is aeolian - in other words, wind-driven. Vast dune fields, intricate rock formations and hazy skies attest to this dry, windy world's nature.

Naturally, science fiction has been quick to jump on the often dramatic storms that, from a distance, look terrifying. Great walls of dust dwarfing the biggest dust or sand storms Earth can muster; bolts of lightning fueled by atmospheric friction; terrible hurricane-force winds that rip up anything in their path, stranding astronauts and destroying hardware...

The movie, based on the best seller by author Andy Weir, is set in the near future during a manned expedition to Mars. A fierce dust storm causes the mission to be abandoned as the astronauts' base station is damaged and one of the crew, Mark Watney (played by Matt Damon) is lost, presumed dead, after being hit by debris, blown away and partially buried by the terrible Martian winds.

But that scene, among others in countless sci-fi imaginings of the Martian environment, is a little misleading, according to NASA scientists, and it all comes down to atmospheric pressure.

Although dust storms on Mars come with their hazards, it's highly unlikely that any storm would be powerful enough to strand astronauts on the surface or rip apart equipment. The strongest Mars winds top out at around 60 miles per hour (less than 30 meters per second), less than half the speed of hurricane-force winds on Earth. But it's not the speed of a wind that does the damage, it's atmospheric pressure, something that Mars is somewhat lacking. The planet's atmospheric pressure is around 1 percent that of Earth's, which is a serious bummer if you wanted to fly a kite on the Red Planet.

"The key difference between Earth and Mars is that Mars' atmospheric pressure is a lot less," said physicist William Farrell, of NASA's Goddard Space Flight Center in Greenbelt, Md., who studies atmospheric breakdown in Mars dust storms. "So things get blown, but it's not with the same intensity."

Although even the most savage dust storm on Mars would likely be the equivalent of a gentle breeze on Earth, Mars dust storms will still cause a problem for our future astronauts, especially if they are dependent on solar power.

In The Martian, Watney spends time every day cleaning solar panels to avoid dust buildup. As has been experienced by our solar powered Mars rovers - particularly NASA's veteran Mars Exploration Rover, Opportunity, that continues to rove over a decade after landing on Mars - this is a very real problem that could seriously limit the collection of solar energy. Also, as the atmosphere becomes filled with fine dust during these storms, the quantity of sunlight reaching the surface is impeded.

"We really worry about power with the rovers; it's a big deal," said planetary scientist Michael Smith, also at Goddard. "The Spirit and Opportunity rovers landed in 2004, so they've only had one global dust storm to go through (in 2007) and they basically shut down operations and went into survival mode for a few weeks."

But it's not just solar panel efficiency the fine dust will interfere with. The electrostatically-charged fine particles are jagged and sharp (as Mars lacks other erosion processes that would smooth these particles), so this dust can cause mechanical issues.

"If you've seen pictures of Curiosity after driving, it's just filthy," Smith added. "The dust coats everything and it's gritty; it gets into mechanical things that move, like gears."

Mars' dusty atmosphere will undoubtedly cause problems for machinery on the surface and there will likely also be health-related problems should we have a long-duration manned mission to the surface (in addition to the increased radiation hazard and toxicity of chemicals in the Martian regolith, or soil). Also, the underlying mechanisms that trigger the most dramatic global dust storms are poorly understood.

"Every year there are some moderately big dust storms that pop up on Mars and they cover continent-sized areas and last for weeks at a time," said Smith "Once every three Mars years (about 5 and a half Earth years), on average, normal storms grow into planet-encircling dust storms, and we usually call those 'global dust storms' to distinguish them.

"It could be that it just takes a while for the sources to replenish themselves. Maybe there's some kind of cycle that the dust has to go through to get back into the right places to trigger a new one, or maybe it's just kind of luck."

Humanity has been observing global dust storms on Mars since 1909 and the last global storm was in 2007, so Mars is overdue its next "big one."

"We're overdue for a global dust storm and it could be saving up a really big one this year, so that would kind of fun," he said. "I like the dust storms."

And with every stormy event on Mars, the more we learn about their processes so we can better prepare for our first human mission to this very dusty, alien planet. But as for the savage storm that strands Watney in "The Martian", rest assured, no one is getting "blown away" by the winds of Mars any time soon.

Mars plays host to a huge number of dune fields -- regions where fine wind-blown material gets deposited to form arguably some of the most beautiful dunes that can be found on any planetary body in the solar system. Using the powerful High-Resolution Imaging Science Experiment (HiRISE) camera on board NASA's Mars Reconnaissance Orbiter, planetary scientists have an orbital view on these features that aid our understanding of

" -- elliptical accumulations of fine material with no-slip surfaces. These domes contrast greatly with the often jagged appearance of barchan dunes. Found at the bottom of Proctor Crater, they are darker than the surrounding crater floor as they are composed of dark basaltic sand that was transported by the wind.

Looking like a wind-blown silk sheet, this field of "star dunes" overlays a plain of small ripples, another aeolian feature. The ripples move more slowly across the bottom of Proctor Crater, so the large dune field will travel

over

the smaller ripples. Dunes are continuously evolving and moving with the wind, ensuring that the Martian surface is never static.

Resembling the mouths of a shoal of feeding fish, this is a group of barchan dunes in Mars' North Polar region. Barchan dunes betray the prevailing wind direction. In this case, the prevailing wind is traveling from bottom right to top left; the steep slope of material (plus dune "horns") point to the downwind direction. The HiRISE camera monitors barchans to see if they move between observing opportunities, thereby revealing their speed of motion across the Martian plains.

...only when zoomed out does the true nature of this fascinating region become clear. The prevailing wind is eroding the mesas (small hills) to the right of the image, carrying fine material downwind (from right to left), creating a startling pattern of barchans and a viscous-looking trail of sandy ridges across the plains.

The band Train sang about the "Drops of Jupiter" -- what about the "Drops of Mars"? Sure, they're not made of any kind of fluid, but they do make for incredibly-shaped dunes. These raindrop-shaped dunes are found in Copernicus Crater and are known to be rich in the mineral olivine, a mineral that formed during the wet history of Mars' evolution.